Update to HarfBuzz 2.9.0

[khaledhosny]

Also re-enable Uniscribe shaper, building it should be fixed now.

[khaledhosny]

I don’t know what to make of the CI build failure on Linux:

Building cp310-manylinux_x86_64 wheel
CPython 3.10 manylinux x86_64

Setting up build environment...
  
      + /opt/python/cp38-cp38/bin/python -c 'import sys, json, os; json.dump(os.environ.copy(), sys.stdout)'
      + which python
  cibuildwheel: python available on PATH doesn't match our installed instance. If you have modified PATH, ensure that you don't overwrite cibuildwheel's entry or insert python above it.
  Error: Process completed with exit code 1.

[khaledhosny]

So building CPython 3.10 wheels is broken on Linux and searching by this error messages nothing comes up, so it suggests we are alone in experiencing this. cibuildwheel is all black magic to me, so I don’t even know where to start debugging this.

[khaledhosny]

The breakage was apparently caused by the forced manylinux1 image instead of using the default. I don’t know the exact cause, but support for manylinux1 will end on January 1st, 2022, so I guess now is a good time to drop it.

[khaledhosny]

Actually the above issue explicitly states that manylinux1 will not support CPython 3.10, so that is our root cause.